" The desire, profound and pitiful, to be appreciated. If that is thwarted, if through an unpleasing personality a human being is unable to get the response it needs, it turns to other methods—it must be felt—it must count—and so to innumerable strange perversions. The habit of cruelty, like any other habit, can be cultivated, can take hold of one— "

― Agatha Christie , Appointment with Death (Hercule Poirot, #17)